Carbohydrate oxidation by leucoplasts from suspension cultures of soybean (Glycine max L.) |
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Authors: | Stephen A. Coates Tom ap Rees |
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Affiliation: | (1) Department of Plant Sciences, University of Cambridge, Downing Street, CB2 3EA Cambridge, UK;(2) Present address: Advanced Technologies (Cambridge) Ltd., CB4 4WA Cambridge Science Park, Cambridge, UK |
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Abstract: | The aim of this work was to discover how leucoplasts from suspension cultures of soybean (Glycine max L.) oxidize hexose monophosphates. Leucoplasts were isolated from protoplast lysates on a continuous gradient of Nycodenz with a yield of 28% and an intactness of 80%. Incubation of the leucoplasts with 14C-labelled substrates led to 14CO2 production, that was dependent upon leucoplast intactness, from [U-14C]glucose 6-phosphate, [U-14C]glucose 1-phosphate, [U-14C] fructose 6-phosphate and [U-14C]glucose+ATP, but not from [U-14C]fructose-1,6-bisphosphate or [U-14C]triose phosphate. The yield from [U-14C]glucose 6-phosphate was at least four times greater than that from any of the other substrates. When [1-14C]-, [2-14C]-, [3,4-14C]-, and [6-14C]glucose 6-phosphate were supplied to leucoplasts significant 14CO2 production that was dependent upon leucoplast intactness was found only for [1-14C]glucose 6-phosphate. It is argued that soybean cell leucoplasts oxidize glucose 6-phosphate via the oxidative pentose phosphate pathway with very little recycling, and that in these plastids glycolysis to acetyl CoA is negligible.S.A.C. thanks the Science and Engineering Research Council for a research studentship. |
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Keywords: | [14C]Glucose 6-phosphate (specifically labelled) Glycine Glycolysis Leucoplast (soybean) Oxidative pentose phosphate pathway |
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